Depression:
Causes of Depression

What Causes Depression?

There is not just one cause of depression. It is a complex disease that can occur as a result of a multitude of factors. For some, depression occurs due to a loss of a loved one, a change in one's life, or after being diagnosed with a serious medical disease. For others, depression just happened, possibly due to their family history.

Factors involved in causing depression, include:

• A history of depression in the family: It is believed that depression is passed genetically from generation to generation, although the exact way this occurs is not known.
• Grief from the death or loss of a loved one.
• Personal disputes, like conflict with a family member.
• Physical, sexual, or emotional abuse.
• Major events that occur in everyone's lives, such as moving, graduating, changing jobs, getting married or divorced, retiring, etc.
• Serious illness: depressed feelings are a common reaction to many medical illnesses.
• Certain medications
• Substance abuse: close to 30% of people with substance abuse problems also have major depression.
• Other personal problems: these may come in the forms of social isolation due to other mental illnesses, or being cast out of a family or social circle.

Biology vs. Emotions

There is absolute proof that people suffering from depression have changes in their brains compared to people who do not suffer from depression. The hippocampus, a small part of the brain that is vital to the storage of memories, is smaller in people with a history of depression than in those who've never been depressed. A smaller hippocampus has fewer serotonin receptors. Serotonin is a neurotransmitter -- a chemical messenger that allows communication between nerves in the brain and the body.

What scientists don't yet know is why the hippocampus is smaller. Investigators have found that cortisol (a stress hormone that is important to the normal function of the hippocampus) is produced in excess in depressed people. They believe that cortisol has a toxic or poisonous effect on the hippocampus. It's also possible that depressed people are simply born with a smaller hippocampus and are therefore inclined to suffer from depression.

Depression is a complex illness with many contributing factors. As doctors gain a better understanding of the cause(s) of the illness they will be able to make better "tailored" diagnoses and, in turn, prescribe more effective treatment plans.

Genetic Link

There is evidence that suggests a genetic link to depression. Children, siblings and parents of people with severe depression are much more likely to suffer from depression than are members of the general population. Multiple genes interacting with one another in special ways probably contribute to the types of depression that runs in families. Scientists have not been able to identify a "depression" gene.

Reviewed by the doctors at The Cleveland Clinic Department of Psychiatry and Psychology.

Edited by Cynthia Haines, MD, WebMD, July 2005.

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Last Editorial Review: 11/28/2005